In the past, there has been proposed a connector interposed between a DC power source and a DC load (e.g. DC device and the like) and used for connecting a line to a cord, or cords to each other. An attachment connector which is one type of the connectors is capable of easily connecting a line to a cord, or cords to each other, by attaching an attachment plug (plug) to a plug receiving equipment, and/or is capable of easily separating a line from a cord, or cords from each other, by detaching the attachment plug from the plug receiving equipment. Especially, a plug receiving equipment which is fixed to a building part such as a wall, a device, or the like is called “outlet”.
For example, Japanese Non-examined Patent Publication No. 2004-31088 discloses a wiring attachment connector including an outlet plug (plug) and an outlet. The outlet plug has a pair of blades (a high potential side blade and a low potential side blade), and the outlet (plug receiving equipment) has blade receiving members in a pair adapted in use to be connected respectively to the blades in the pair of the plug. Further, aforementioned Japanese Non-examined Patent Publication discloses the outlet has a blade insertion slot shaped into a shape where an existing insertion plug for AC power can not be inserted.
Although an AC power source alternates a high potential side (e.g. a positive electrode) and a low potential side (e.g. a negative electrode) periodically, a DC power source does not alternate a high potential side and a low potential side. Meanwhile, a DC load has a terminal for connecting to the high potential side of the DC power, and a terminal for connecting to the low potential side of the DC power. The DC load is activated by voltage applied between the aforementioned terminals.
In short, the DC load has polarity. Therefore, a user need be careful not to cause improper wiring (or improper connection) where the high and low potential sides are connected inversely, when the user connects an outlet to a DC power or connects an outlet plug to an outlet. When the high and low potential sides are connected inversely, inverse voltage is applied between the terminals of the DC load. The inverse voltage gives a stress to the DC load, and the DC suffering from the stress is likely to break.
However, when a user connects respectively two feeder wires (DC supply lines) of a DC power to terminals in a pair (a pair of terminals electrically connected to a pair of blade receiving members) of an outlet, the user is likely to connect the feeder wires to the terminals with inverting the high potential side and the low potential side. In short, the low potential side terminal of the outlet is likely to be connected to the high potential side feeder wire, and the high potential side terminal of the outlet is likely to be connected to the low potential side feeder wire.
When an outlet has blade receiving members or blade insertion slots having the same shape as each other, it is difficult to distinguish between polarities of each of the blade receiving members with reference to an exterior appearance. Therefore, though a user intends to connect a device to the information outlet having the terminal receiving member receiving DC power, the user is likely to mistakenly connect the device to the information outlet having the terminal receiving member not receiving DC power.
As described in the above, in the conventional outlet or connector, the improper wiring is likely to give harmful effect to a DC device.